常见问题

To avoidmechanicalandtemperature-relateddamagestwo kinds oflimiterscan be used:

• RMS limiter:Protectsspeakersagainst thermal damage whenexcessivepoweris applied for extended periods of time, resulting inoverheating, and eventuallyburning. Designers should be aware of the maximum long-term power safely applicable to speakers (AES power rating). An interesting approach to RMS limiting is one that uses coil temperature control looking at how the peak in the impedance curve changes when the speaker starts heating.

Infigure 3we can see the relationship between the temperature and impedance curves: the green curve is the curve measured when the speaker is at 26°C, meaning it is cold. The orange curve is when the temperature increases to 38°C. We can notice that when the speaker starts heating up the impedance peak will become higher in value and will shift slightly in frequency. Therefore, being able to monitor the impedance changes in real-time will allow us to save our loudspeaker. Complete knowledge of the driver’s limits allows for keeping the temperature level in a safe interval not only to avoid damage.

Live impedance curves

• Peak and limiter: Protect against mechanical damages. Designers should set these limiter parameters as a function of both the maximum displacement (XMAX) of the diaphragm and the speaker's maximumtoleratedvoltage.

NOTE: Relying on peak limiting only for speaker protection can still lead to excessive long-term average power and consequential damages.